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Message-ID: <20220208154931.4371-1-xiezhipeng1@huawei.com> Date: Tue, 8 Feb 2022 10:49:31 -0500 From: Zhipeng Xie <xiezhipeng1@...wei.com> To: <peterz@...radead.org> CC: <acme@...nel.org>, <alexander.shishkin@...ux.intel.com>, <jolsa@...hat.com>, <linux-kernel@...r.kernel.org>, <linux-perf-users@...r.kernel.org>, <mark.rutland@....com>, <mingo@...hat.com>, <namhyung@...nel.org>, <xiezhipeng1@...wei.com>, <xiexiuqi@...wei.com>, <fanwentao@...wei.com> Subject: Re: [PATCH] Fix perf_mmap fail when CONFIG_PERF_USE_VMALLOC enabled On Mon, February 7, 2022 10:12 PM, Peter Zijlstra wrote: > Your $Subject needs a subsystem prefix. Thanks for your comments, I will adjust the patch Subject and resend the patch according to your suggestions. > On Mon, Feb 07, 2022 at 12:02:59PM -0500, Zhipeng Xie wrote: > > when CONFIG_PERF_USE_VMALLOC is enabled, rb->nr_pages is always > > equal to 1 in rb_alloc, causing perf_mmap return -EINVAL when mmap. > > Fix this problem using data_page_nr. > > How can this be? This would mean that any arch that selects that hasn't > worked for forever ?! That seems unlikely. Arch with CONFIG_PERF_USE_VMALLOC enabled by default: arc/arm/csky/mips/sh/sparc/xtensa Arch with CONFIG_PERF_USE_VMALLOC disabled by default: x86_64/aarch64/... I have this problem when using sysdig -B(using ebpf)[1] on an aarch64 kernel with CONFIG_PERF_USE_VMALLOC enabled. sysdig -B works fine after rebuilding the kernel with the CONFIG_PERF_USE_VMALLOC disabled. I tracked it down to the if condition event->rb->nr_pages != nr_pages in perf_mmap is true where event->rb->nr_pages = 1 and nr_pages = 2048 resulting perf_mmap to return -EINVAL. [1] https://github.com/draios/sysdig > > Signed-off-by: Zhipeng Xie <xiezhipeng1@...wei.com> > > If this is correct; this is also missing a Fixes: tag. Sorry, I don't know when this problem was introduced, so I have no idea which commit my patch fixes.from the git log, this problem seems to have existed for a long time, even before the ebpf feature was introduced.
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